解法一：Map

频率统计。

#include <bits/stdc++.h>
using namespace std;
int main() {
    int M, N;
    cin >> M >> N;
    int tmp;
    map<int, int> cntMap;
    for (int i = 0; i < N; ++i) {
        for (int j = 0; j < M; ++j) {
            cin >> tmp;
            auto res = cntMap.find(tmp);
            if (res == cntMap.end()) {
                cntMap.emplace(tmp, 1);
            } else {
                res->second += 1;
            }
        }
    }
    int maxKey = 0;
    int maxVal = 0;
    for (auto &item:cntMap) {
        if (item.second > maxVal) {
            maxKey = item.first;
            maxVal = item.second;
        }
    }
    cout << maxKey << "\n";
}